The present invention relates generally to mobile communications, and more specifically to base stations used in mobile communications.
Mobile communications are implemented by means of appropriate network architecture. FIG. 1 shows a high level block diagram of an exemplary mobile network architecture. In FIG. 1, device 102 is a wireless mobile device that can communicate with first base station 104. Usually, a multiplexing technology is used for such access, such as, for example, Code Division Multiple Access (CDMA), Time Division Multiplexing (TDMA), etc. The network includes the first base station 104, a second base station 106, and a third base station 108. Each base station 104, 106, 108 has a transmission range that defines a cell 110, 112, 114. Any given base station transmits and receives mobile calls via the cell's antenna. Thus, a wireless mobile device located within a given cell transmits and receives call information to/from the base station associated with that cell.
Each base station 104, 106, 108 communicates with, and is controlled by, a mobile switching center (MSC) 116. The MSC 116 switches calls between the cellular network and the public switched telephone network (PSTN) and vice versa. For example, consider landline telephone 120 connected to central office (CO) 124. The CO 124 communicates with the MSC 116. When a user of the landline telephone 120 calls mobile device 102, the call is routed to the MSC 116 in a well known manner. A typical MSC is aware of the cell location of all mobile phones and directs the call to the first base station 104 because the mobile device 102 is located in the first cell 110.
FIG. 2 shows a more detailed block diagram of a traditional base station 200. The base station 200 includes a plurality of radios, such as a first radio 204, a second radio 208, and a third radio 212. Each radio 204, 208, 212 generates transmission signals having a particular frequency to be transmitted to a mobile device and also analyzes/processes signals received by the base station from the mobile device. The signal generated by each radio 204, 208, 212 is first sent to a respective power amplifier (PA) 220, 224, 228 for amplification before the signal is transmitted to a mobile device. An output signal (the amplified signal) of each PA 220, 224, 228 is transmitted to an Antenna Interface Frame (AIF) 232.
In more detail, an output signal (e.g., a first output signal 236) is transmitted from a PA (e.g., first PA 220) to a transmit combiner 240 of the AIF 232. The transmit combiner 240 combines the output signals from the PAs 220, 224, 228 into a single output signal 244. The single output signal 244 has a power that is the summation of the powers (i.e., the signal spectra) associated with the output signal of each PA 220, 224, 228. The output signal 244 of the transmit combiner 240 is then provided as input to a central duplexer 248 of the AIF 232.
The central duplexer 248 is a device that isolates a transmit signal path 252 from a receive signal path 256 while permitting them to share a common antenna 260. The duplexer 248 can combine communication signals onto a single cable for transmission by the antenna 260. The duplexer 248 can also filter the signals before sending or receiving signals to/from the common antenna 260. The central duplexer 248 is designed for operation in the frequency band used by the receiver 256 and the transmitter 252, and is capable of handling the output power of the output signal 244 of the transmit combiner 240.
The receive path 256 of the central duplexer 248 passes a receiver signal 264 to a receive splitter 268. The receive splitter 268 splits the receiver signal 264 into a plurality of radio signals (e.g., radio signal 272) that are each associated with a corresponding radio (e.g., radio 212).
The design of a traditional base station, such as base station 200, has several drawbacks. First, base stations (e.g., base station 200) typically have a complex and costly AIF that hosts many components including the central duplexer. When additional radios and PAs are added to a base station, additional transmit combiners and receive splitters often have to be added to the AIF.
Second, the duplexer is a central element whose power capacity is designed to meet the maximum capacity (equal to the maximum number of radio frequency (RF) carriers (e.g., radios)) of a base station. To illustrate, suppose an operator of a mobile network has a need to handle three carriers. The operator purchases a base station that can handle the required three carriers from a seller of base stations. At a later point in time, the operator may determine that the operator needs to add a fourth carrier to the capacity of the base station. The operator then has to upgrade the base station by purchasing an additional radio and an additional PA. The central duplexer, however, is not replaced because the duplexer in the base station has to be able to handle the maximum number of carriers of the base station. Therefore, the AIF (and therefore the base station itself) typically has a high entry cost (i.e., with initial deployments, there are costs associated with the final (i.e., maximum capacity) configuration after capacity upgrades are made) because of the cost associated with the initially deployed central duplexer. Thus, a typical operator pays for a central duplexer that can handle the maximum capacity of the base station when the operator initially purchases the base station. This traditionally results in a high, up-front cost for the operator.
Third, base stations also often have separate printed circuit boards (PCBs) (also referred to as Maintenance Replaceable Units, or MRUs) for the radio, PA, and AIF. Even if one or more of the radio(s) and PA(s) are integrated into a single PCB (i.e., MRU), the AIF is typically located with a separate PCB (i.e., MRU). Therefore, someone who maintains a base station may need to have all of the PCBs (MRUs) associated with the different components of the base station. Further, when an owner of a base station decides to upgrade the base station for more capacity or other enhanced features, the owner typically has to replace multiple MRUs.
Therefore, there remains a need to solve many of the shortcomings associated with traditional base stations.